A motorized vehicle such as a plug-in hybrid electric vehicle (PHEV) and an electric vehicle (EV) that is mounted with an AC/DC converter for converting AC (alternative current) voltage supplied from a commercial power source for home use into DC (direct current) voltage and charges its battery with the converted DC voltage converted by the AC/DC converter has been in widespread use.
In recent years, expectations run high that a battery for a motorized vehicle such as a plug-in hybrid electric vehicle and an electric vehicle is utilized for disaster or emergency power supply. In order to utilize the battery as an emergency power supply, bidirectional conversions from AC voltage to DC voltage and from DC voltage to AC voltage are required.
Japanese Patent Application Publication Laid-Open No. 2013-247817 discloses a charger control system (corresponding to a bidirectional AC/DC conversion apparatus) that performs bidirectional conversions between AC voltage from an AC power source and DC voltage from a battery. The charger control system includes a power factor correction (hereinafter referred to as PFC) circuit having a power factor correcting function upon charging and discharging of a battery and an isolated bidirectional DC/DC converter that is cascade-connected to the PFC circuit.
The DC/DC converter includes two full bridge circuits provided on the primary and the secondary sides of a transformer, each of which functions as a DC/AC inverter and a rectifier circuit. More specifically, upon charging of the battery, the full bridge circuit on the PFC circuit side and the full bridge circuit on the battery side respectively function as a DC/AC inverter and a rectifier circuit while upon discharging of the battery, the full bridge circuit on the battery side and the full bridge circuit on the PFC circuit side respectively function as a DC/AC inverter and a rectifier circuit.
In a conversion apparatus similar to that disclosed in Japanese Patent Application Publication Laid-Open No. 2013-247817, a total sum of circuit losses of the PFC circuit and the DC/DC converter decides conversion efficiency as a whole.
Hereupon, in order to optimize the conversion efficiency of the whole system, Japanese Patent Application Publication Laid-Open No. 2013-247817 describes the charger control system having a configuration in which the DC voltage to be outputted and inputted from the PFC circuit is optimized upon charging and discharging of the battery, but merely describes the power factor correction (PFC) itself within the range of the well-known art.